The entire back surface of a conventional crystalline silicon solar cell is usually printed with aluminum paste. There are some weaknesses in the all-aluminum back surface field structure, such as low back surface reflectivity, weak long wavelength photon absorption, and high recombination rate of photo-induced charge carriers at the back surface of a solar cell, and thus, the electrical performance of a solar cell is affected by these weaknesses. Improving the quality of surface passivation and decreasing the surface recombination rate have become main methods to improve the efficiency of the solar cells. PERC (Passivated Emitter Rear Contact) silicon solar cells are a special type of conventional crystalline silicon solar cells, characterized in that medium passivation layers exist both on the front surfaces and on the back surfaces of the solar cells.
As for efficient bifacial point contact crystalline silicon solar cells, laser technology is used to notch on the back surface medium layer, so as to bare filiform or punctiform silicon substrate. Aluminum paste is screen printed on the notched area of the medium layer, while the entire back surface is not covered by the aluminum paste.